Throttle control device for aircraft engines



y L. s. GREENLAND THROTTLE CONTROL DEVICE FOR AIRCRAFT ENGINES Filed April 1-0, 1944 4 Sheets-Sheet 1 BOOST PRESS URE OPENING-UP STAGE E LJILIBRILJM AT CRUISING soos'r;

y 1945- L. s. GREENLAND 2,376,690

THROTTLE CONTROL DEVICE FOR AIRCRAFT ENGINES Filed April 10, 1944 t 4 Sheets-Sheet 2 OLD TYPE LINKAGE. NEW TYPE LINKAGE FULL- Full k 48 I Q Q g 30 16! i ,I L val.

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y 1945- L. s. GREENLAND THROTTLE CONTROL DEVICE FOR AIRCRAFT ENGINES Filed A ril 10, 1944 4 Sheets-Sheet 3 May 22, 1 945. 5 GREENLAND 2,376,690

THROTTLE CONTROL DEVICE FOR AIRCRAFT ENGINES Q MEMQIQMQMQ w Patented May 22, 1945 THROTTLE CONTROL DEVICE FOR AIRCRAFT ENGINES Leonard Sidney Greenl asslgnor to H. M. Ho Components Limited,

and, Coventry, England, bson (Aircraft & Motor) London, England Application April 10, 1944, Serial No. 530,428 7 In Great Britain April 3 Claims. (Cl. 123-119) This invention relates to throttle controls for aircraft engines of the kind, described for example in U. S. Patent No. 1,995,800, in which the servo piston of a variable datum boost control device Varies the setting of a mechanical linkage interposed between the pilots throttle lever and the throttle valve in such a way as to prevent excessive opening of the throttle valve.

Such apparatus has hitherto been used on engines fitted with a float type carburetter and it has been the invariable practice to construct the linkage in such a way that movement of the pilot lever from slow running to cruising boost produces a large opening of the throttle valve, e. g. 60 or more. the boost control device acting below the full throttle height, i. e. the altitude at which cruising boost (C. B.) can be sustained only with full throttle, to reduce the throttle movement produced manually by the action of the pilots lever. Due to its construction, this arrangement has the disadvantage that, as explained below, at certain positions of the pilots lever for altitudes greater than the full throttle height, the throttle valve is restrained short of its full opening although the boost pressure in the induction manifold may be less than the value selected by the position of the pilots lever. Under these conditions, the maximum height to which a selected boost pressure can be maintained is less than that obtainable when the throttle valve is permittedto reach its full open position.

According to the invention the linkage between the pilots lever and the throttle valve is so arranged that movement of the pilots lever from slow running to cruising boost is only effective to move the throttle valve through a relatively small angle, e. g. about 10. The major portion of the required movement of the throttle valve is communicated by the servo piston of the boost control device, said piston being under the influence of a servo valve which is controlled from the pilots throttle lever through a barometric element exposed to boost pressure.

In the accompanying drawings,

Figs. 1, la and 2 are respectively diagrammatic showings of the layout of a linkage accord- .ing to the invention, showing successive stages in the operation of theparts as the pilots lever is moved to open the throttle,

Figs. 3-8 are graphs affording a comparison be- 4 tween the old linkage (Figs. 3, 5 and 7) and the new linkage (Figs. 4, 6 and 8).

Figs. 9 and 10 are diagrammatic showings of two alternative forms of throttle linkage according to the invention, and

Fig. 11 is a, detailed drawing of a preferred linkage according to the invention.

It will be understood that Figs. -1, 1a and 2 are diagrams only, the servomotor not beingshown in detail in these figures. In each case, however, the

servomotor is of the construction shown in Fig. 11 and is operated insimilar fashion by the capsule responsive to boost pressure.

Figure 1 represents the conditions at slow running, Fig. 1a those prevailing immediately after the pilots lever has been moved to the cruising boost position and Fig. 2 those prevailing after the servo motor has come into operation. In each figure, lll represents the pilots lever, It the throttle valve, l2 a toggle linkage connecting them, it the variable datum cam, Hi the capsule of the boost control device, 85 the servo piston of the latter and (6 a spring associated with the servo piston. In the case of the new linkage, a toggle is not ordinarily employed, but a toggle which is the equivalent of the actual linkage is shown in Figs.

1, 1a and 2'. In each of these figures, the servo cylinder is shown disposed' vertically, and reference is hereinafter made to the top and bottom ends of the cylinder. It will be understood, however, that the servo cylinder may be disposed horizontally or in any other convenient position.

In the case of the known linkage, the servo piston is caused to move to the bottom end of its cylinder at slow running, and the throttle valve is closed under these conditions, the linkage connecting the pilots throttle lever and the throttle valve being straight.

On moving the pilots lever to the cruising boost position, the first action is for the linkage to open the throttle valve l l mechanically to a wide angle, the piston remaining at the bottom of its cylinder. Then, when the relay mechanism has had time to operate, pressure oil is admitted to the underside of the piston, so causing the latter to rise towards the top end of the cylinder, break the linkage and close the throttle valve M to obtain the desired boost.

As altitude increases, with the pilots lever remaining in the same position, the boost control will operate to force the piston progressively down to the bottom position. At the full throttle height the piston will reach the limit of its travel and the throttle will be fully open. Above this height a lower boost than cruising boost will be obtained with the pilots lever at the cruising boost position and the throttle fully open, and when the pilots lever is moved towards the closed position at such a height the boost will progressively reduce (as later explained with reference to Fig. 5) by virtue of the straight linkage.

In the case of the linkage according to the invention, the leverage ning, thus breaking the linkage I? (see Fig. 1). This is because the cam i3 is shaped to direct high pressure oil to the underside of the piston at low throttle openings and thus ensure that the piston is inoperative.

On movement of the pilots lever to the cruising boost position, Fig. 1a, the linkage I2 remains toggled and due to the decreased leverage the manual movement 50 imparted to the throttle valve can only open it by a small amount, say 10.

Bnmediately afterwards the relay mechanism comes into action, the piston l5 descending in its cylinder, thereby straightening the linkage and opening the throttle until the required boost ,is obtained, Fig. 2.

As height is increased with the pilots lever in this position, the servo piston will continue to descend and straighten the linkage until, at full throttle height, the throttle becomes fully openi If at any height near the full throttle height, the pilot moves his throttle lever towards the slow running position, he will only close it manually by a few degrees, which will have no appreciable effect on-boost pressure, and the remaining closing of the throttle will be obtained by toggling of the linkage via, the servo piston.

At the time that the variable datum boost control described in U. S, Patent'No. 1,995,800 was developed, the boost pressure in all aircraft engines then known increased progressively with the throttle opening as the throttle valve was opened from the slow running position. In the case, howversal, the point of manual control must, in order or avoid the above-indicated disadvantage, be located outside the range ofboost reversal, i. e. it must represent a position of the pilots lever coinciding with or somewhat more open than the upper. limit of the range of boost reversal.

The advantages gained with the new linkage will be appreciated by reference to Figs. 3-8 of ever, of more recent types of aircraft engine, which have a considerable degree of valve overlap, the phenomenon of boost reversal occurs at low throttle opeings. With such engines the boost pressure is higher when the pilots lever is at slow running than when it has been moved slightly away from this position in the direction to open the throttle. If, therefore, a variable datum cam, designed to give a progressive diminution of boost as the throttle closes, is used and so coupled to the throttle that the servo mechanism is in operation throughout the range of movement of the pilots lever, the result would be that at slow running the engine would, due to thevalve overlap, be receiving an actual boost pressure in excess of that called for by the cam. When the pilots lever is moved from the slow running position, the actual boost will fall, and the servomotor will not be effective to open the throttle until the boost has risen again, due to continued mechanical opening by the pilots lever, to a value just in excess of that prevailing at slow running. There will then be a sudden surge of power due to the sudden opening of the throttle, which renders fine control of the engine at low powers impossible.

, lever is moved on into the slow running position,

so that the throttle is operated by the mechanical linkage only between slow running and the point of manual control.

In the case of an engine subject to boost rethe drawings. the relationship between throttle valve opening and pilots lever position for the old and new linkages respectively, and Figs. 5-8 are similar graphs showing the relationship between boost pressure, throttle angle and pilots lever position, Figs. 5 and 7 relating to the old linkage and Figs. 6 and 8 to the new linkage.

For purposes of comparison with the new linkage, it is assumed in Figs. 3, 5 and 7 that, in the case of the old linkage, the servo mechanism is likewise placed out "of action when the pilot's lever, on moving to close the throttle, reaches the point of manual control.

These advantages can be explained as follows:

1. Increased power at height By comparison of the curves in Figs. 3 and 4,

it is revealed that for pilots lever positions between the point of manual control (1. e. the position of the pilots lever at which, as the lever is moved to close the throttle, the servo piston of the boost control device is brought to a stop at the end of its cylinder, this point being indicated at B in Fig. 3 and at A in Fig. 4) and that of C. B., a larger throttle valve opening is available above the full throttle height with the new linkage, as indicated by the shaded zone in Fig. 4. This means that selected boosts within the cruising range can be sustained to greater heights, the limit being reached only when the throttle has attained the full open position. For installations where engine R. P. M. and boost pressures are mechanically interconnected, this represents an economy, it being'understood that the best economy for a given power is obtained when the R. P. M. are lowest. Figs. 5 and 6 show the boost pressures relating to the conditions shown in Figs.

3 and 4.

' fixed fulcrum 20.

2. Improved control at low powers With high powered aero-engines in use at the present time, small movements of the throttle valve produce relatively large changes in engine power which can present difficulties during taxi ing. By virtue of the reduced lever ratio shown in Figs. 1, 1a and 2, it will be appreciated that a very slow opening of the throttle valve over the manual range is obtained for a relatively large movement of the pilots lever, thus giving the pilot improved control for taxiing the aircraft.

This efiect is illustrated in Fig. 8 by the slope of the-line 0A which indicates that for a given movement of the pilots lever, the change of throttle opening with the new linkageis less than that with the old type which is represented by line QB other than that shown in Figs. 1, 1a and 2. Two

such arrangements are shown diagrammatically in Figs. 9 and 10 of the drawings.

In the arrangement shown in Fig. 9, the pilots lever HI carries a cam I1 cooperating with a roller l8 carried by'a bell crank l9 pivoting on a The other arm or the bell crank ispivoted to a rocking lever 23 connected Figs. 3 and 4 are graphs showing at one end to the piston rod M or the servo piston l8 and at the other by a link 22 to the throttle valve H; The servo piston, as in the case of Figs. 1, 1a and 2, is associated with a spring l5 operating to urge it towards the slow running position.

In the scheme shown in Fig. 10, the servo piston 16 operates the throttle valve ll via a linkage incorporating a rocking lever 23 pivoted on an eccentric shoulder 24 carried on the layshaft 25 fixed to the pilots lever l0. Thus, with the servo piston l6 stationary, the action of the eccentric shoulder 24 within the rocking lever 23 is to produce a small opening of the throttle valve ii for a large movement of the pilots lever i ll.

With both these arrangements, the servo piston I5 is free to override the pilots lever I ii and adjust the throttle opening to obtain the boost selected.

The major part of the available manual opening is communicated to the throttle valve during the range of boost reversal, Where of course, the servo mechanism is inoperative. It is preferred, however, to arrange that a small amount of manual opening is extended over the remaining movement of the pilots lever in order to avoid a sudden discontinuity as between manual and servo operation when the servo mechanism comes into action as the lever moves out of the slow running range, see Figs. 7 and 8.

When desirable, the throttle opening we. the

latter portion of the lever movement can be such as to provide a reasonable degree of power in the event of servo failure through lack of fluid pressure.

3. Reduced operating loads The passage of air past the throttle valve creates a closing torque on the throttle spindle which is transmitted back through the operating linka e in. the nature of a direct load on the pilots lever. With high powered engines employing large multiple throttles, this loading can become a serious problem.

Withthe old type of linkage which had manual over-opening and servo,closing,.the effort needed at the pilots lever in order to open the throttles, was considerable.

The improved leverage of the new linkage decreases the efiort needed at the pilots lever over the manual range, i. e. up to position A in Fig. 8, and from this point onwards, the greater portion of the throttle movement isaccounted for by the servo piston and consequently, the load on the pilots lever is quite small.

4. I mprooed acceleration main fuel system. With the new linkage this condition cannot occur due to the limit imposed on the extent of manual throttle opening. The

defect can be remedied by us ng a large acceler-" ator pump, but of course, the type of linkage giw'ng the required engin acceleration with only small assistance from the accelerator pump is to bepreferred. v

When an injector of the type described in copending application Serial No. 494,514 is fitted with a boost control linkage according to the invention as shown in and hereinafter described with reference to Fig. 11, the movement or the pilots lever during acceleration simultaneously increases the area of the fuel metering port. This gives a lead to the fuel because of the slight lag in the operation of the servo mechanism and results in a rich mixture during acceleration which is desirable.

It will be understood that a remote'acting fluid pressure system may be used for transmitting the movement of the pilots lever to the throttle valve, e. g. a system of the type described in British Patent No. 483,049. The linkage according to the present invention will then be incorporated between the servo piston of the receiver unit of said fluid pressure system and the throttle valve.

In Fig. 11 is shown in greater detail, by way of example, one specific embodiment of throttle control according to the invention.

In this figure, the parts are shown in full lines in the positions they occupy with the pilots lever 38 in the slow running position. The chaindotted lines show the efiect of manual opening of the throttle valve Si by movement of the pilots lever into the cruising boost position, the parts being shown in the positions they occupy before the boost control has had time to operate. 4

The pilots lever W has fixed to it a shaft ti mounted to turn in bearings (not shown). On

the shaft 36 are fixed an eccentric 32 and a cam 33. Surrounding the eccentric 32 is a yoke 34%, pivoted at one end to a link 35 connected to the throttle valve 6i and at the other end to a link it, pivoted at its lower end it to the piston rod of the servo piston M of the boost control device.

As will be seen, manual opening of the throttle, on movement of the pilots lever from the slow running tothe cruising boost position i effected by bodily movement of the eccentric 32, the link it rocking about its lower pivot 33. This manual opening by the mechanical linkage between the pilots lever and thethrottle valve is small, as shown, being only about 10.

The cam 33, which is the variable datum cam, has a cam slot 39 engaged by a roller 59 mounted on. a link it. A slot M at the upper end of the link it engages a circular bOSs (not shown) on the shaft ll and guides the link in the up and down movements communicated to it by the cam.

The lower end of the link lit is connected by intermediate links Ma, 52 to the left hand end of a cross link as. This cross link is pivoted centrally to a rod M connected at its upper end to the capsule 35 of the boost control device and at its lower end to a sleeve 36 forming part of a variable-area fuel metering orifice through which fuel is pumped to the engineas described and claimed in co-pending application Serial No.

494,51d. The right hand end of the cross link it is pivoted to the piston rod of a normally inoperative resettlng piston ll which however. operating against its upper spring Qt provides a correction in the fuel flow in the-range of boost reversal and, operating against its lower spring is corrects the fuel flow above full throttle height.

The capsule i5 is mounted in an enclosure 56 exposed to boost pressure through a conduit ti. and is attached at its upper end to a control valve 52. This controls in known manner the connections between a pressure inlet 53, exhaust outlets 5d and the cylinders of the two servo pistons 31, fll.

'It is clear that movement of the pilots lever from slow running to cruising boost will raise the left hand and of the cross link 43, so lifting the capsule 45 and control valve 52 and directing pressure oil to the upper side of the servo piston 3'8. This will therefore move down, rocking the yoke 34 clockwise about the eccentric 32 and openingthe throttle valve to a position such that cruising boost is obtained, the resulting contraction of the capsule 45 returning the control valve 52 to its neutral position, and causing the downward movement of the se piston 37 to cease. Under normal conditi ns, i. e. below full throttle height, the resetting piston 4i is inoperative, being maintained in the position illustrated by its spring 49. This spring is stronger than the spring associated with the main servo piston 31 so that when pressure oil is admitted to the upper ends of the two cylinderswhich occurs when" there is a fall in boost-the main servo piston 3'5 only will be depressed. Depression of this piston results in opening movement of the throttle. When, however, full throttle height is reached the piston 31 reaches the bottom of its cylinder, and above this height the engine is unable to maintain the selected boost when the pilots lever is in the full throttle position. The resultant expansion of the capsule, however, results in admission of pressure oil to the upper end of the cylinder housing the resetting piston. This then moves down against its spring 49 to reduce the area of the fuel metering orifice and so adjust the fuel flow to conform with the reduced boost.

Under normal conditions due to the fact that the spring 49 is stronger than the spring 55, the resetting piston 41 has no influence on the capsule, the link 43 pivoting about its right-hand end which remains stationary. When the resetting piston moves down above full throttle height the link 43 pivots about its left-hand end.

When the pilots lever is at or near slow run ning and the servo piston 31 is held inoperative in its upper limiting position, an increase in boost due to boost reversal causes admission of pressure fluid to the under surface of piston 41, which then rises against its spring 48 to open the metering orifice somewhat and adjust the fuel flow to.

suit this increase in boost. Under ordinary conditions in which piston 31 is free to rise, the spring 48 will prevent the resetting piston 41! from moving.

The resetting piston forms no part of the resent invention and is only illustrated to complete the showing of the whole installation. It comes into operation only under the two specific abnormal conditions referred to, i. e. above full throttle height when it reduces the fuel flow to compensate for the fact that selected boost cannot be maintained, and below the point of manual control when it increases the fuel flow if the boost risesdue to boost reversal.

The cam slot 39 is so shaped that, when the roller 59 reaches the point marked X on movement of the pilots'lever towards the slow running position, the servo piston 31 reaches the top or slow running end of its cylinder, while on continued movement of the pilots lever towards the slow running position, the servo piston 31 re-; mains at the top of its cylinder and the servo motor is therefore inoperative. the pilots lever at which the roller 59 is at the point X of the cam slot 39 is the position here inbefore referred to as the point of manual control and corresponds'to the upper limit of the range of boost reversal.

Almost the whole of the manual movement communicated to thethrottle valve by the me- The position of.

chanical linkage from the pilots lever takes place during movement of the pilots lever over the range from the slow running position to the point of manual control. A small residual manual movement is however imparted to the throttle valve by movem ent of the pilot's lever over the range from the point of manual control to the cruising boost position, as indicated in Fi 8.

It will be understood that the terms piston and cylinder as used herein are intended to comprehend the functionally equivalent elements of a vane type motor, as disclosed for example in Serial No. 551,703 of Stanley V. Maddox for Servomotors.

I have described what I believe to be the best embodiment" of my invention. I do not wish, however, to be confined to the embodiment shown, but what I desire to cover by Letters Patent is set forth in the appended claims..

What I claim as my invention and desire to secure by Letters Patent is:

, and said throttle valve for operating the throttle 'and wherein the servo mechanism is rendered valve on movement of the lever, and a variable datum boost control device including a servo valve, a barometric control member therefor, an operating connection from the pilot's throttle lever to the barometric control member and a servo piston, movable in a servo cylinder, and arranged to vary the setting of said'linkage so as to prevent excessive opening of said throttle valve, wherein movement of the pilotfs throttle lever from the slow running to the cruising boost position imparts, through the agency of said mechanical linkage, a relatively small manual opening movement only to the throttle valve, the major portion of the movement of said throttle valve into the position to establish cruising boost being communicated thereto by the servo piston,

inoperative through attainment by the servo piston of that limit of movement in its cylinder toward which said servo piston moves on moving to close the throttle valve when the pilots throttle lever, on movement to close the throttle, reaches the point of manual control, movement of the throttle valve as the pilots throttle lever moves between the point of manual control and the slow running position is effected solely through i the agency of said mechanical linkage.

2. A throttle control for an aircraft engine,

, comprising in combination a throttle valve, a

pilots throttle lever movable between a slow running and a cruising boost position, a mechanical linkage interposed between 'said lever and said throttle valve for operating the throttle valve on movement of the lever, and a variable datum V boost control device including a servo piston arranged to vary the setting of said linkage so as to prevent excessive opening of said throttle valve, and. control means for the servo piston, wherein movement of the pilots throttle lever from the slow running. to the cruising boost position imparts, through the agency of said mechanical linkage, a. relatively small manual opening movement only to the throttle valve, the major asv coo' portion of the movement of said throttle valve into the position to establish cruising boost being communicated thereto by the servo piston, said linkage between the pilots throttle lever and the throttle valve comprising an eccentric fixed to the pilots throttle lever and rotatable by movement of said lever, a yoke pivotally mounted on said eccentric, and a linkage connecting one end of the yoke with the throttle valve, and said variable datum setting boost control device including a linkage connecting the opposite end of the yoke with the servo piston control means, manual movement being communicated to the throttle valve from the pilot's throttle lever by rotation of saldeccentric, and sen/o movement being communicated to said throttle valve .by rotation of said yoke about said eccentric.

3. A throttle control for an aircraft engine, exhibiting the phenomenon of boost reversal at small throttle openings, comprising in combination a throttle valve, a pilots throttle lever movable from a slow running position, through a point of manual control near to said slow running position and on to cruising boost position but outside the range of boost reversal, a mechanical linkage interposed between said lever and said throttle valve for operating the throttle valve on movement of the lever, and a variable datum boost control device including a servo valve, a barometric control member therefor, an operating connection from the pilot's throttle lever to the barometric control member and a servo piston, movable in a servo cylinder, between a slow running position at one end thereof and a full throttle position at the other end thereof and arrangedto vary the setting of said linkage so as to prevent excessiv opening of said throttle valve, wherein movement of the pilot's throttle lever from the slow running to the cruising boost position imparts, through the agency of said mechanical linkage, arelatively small manual opening movement only to the throttle valve, the major portion of the movement of said throttle valve into the position to establish cruising boost being communicated thereto by the servo piston.

wherein the servo mechanism is rendered inoperative by movement of the servo piston to the slow running end of the servo cylinder when the pilot's throttle lever, on movement to close the throttle, reaches th point of manual control, the connection from said pilot's throttle lever to the barometric control member being constructed and arranged to prevent operation of said piston away from said slow running end of the servo cylinder as the pilots throttle lever moves between the point of manual control and the slow running position, so that movement of the throttle valve as the pilot's throttle lever moves between the point of manual control and the slow running position is effected solely through the agency of said mechanical linkage, wherein the major portion of the manual opening movement is communicated to the throttle valve by movement of the pilots throttle lever over the range from the slow running position to the point of manual control. but wherein a small additional manual movement is imparted to the throttle valve by movement of the pilot's throttle lever between the point of manual control and the cruising boost position.

LEONARD SIDNEY GREENLAND. 

